What is the ideal ergonomic design for your work situation? The
following questions will help you decide.
How will the
computer be used?
If only one person will be using the computer then the arrangement can be optimized
for that persons size and shape. An adjustable height chair, for instance,
may be unnecessary. If several people must use the computer, youll need
to create an arrangement that most closely satisfies the needs of the extremes
the smallest and tallest, thinnest and broadest persons. Also think about
how long people will be using the computer. A few minutes wont make ergonomic
issues a high priority. More than one hour each day, though, may require an
What kind of computer will be used?
Ergonomic guidelines assume that youll be using a desktop system with
the computer screen separated from the keyboard. Guidelines for laptop use are
more difficult because laptop design inherently is problematic when the
screen is at a comfortable height and distance, the keyboard isnt and
vice versa. For sustained use you should consider purchasing either an external
monitor or an external keyboard and a docking station.
What kind of work will the computer
be used for?
Try to anticipate the software and activity to be used most often.
arranging the best keyboard/mouse position is high priority
Browsing the Internet/graphic
design arranging the best mouse position is
arranging the best numeric keypad/keyboard is high priority
arranging the best keyboard/mouse/game pad is high priority
Where should the computer monitor
The monitor should be:
||Directly in front of the user and facing
the user, not angled to the left or right, to avoid neck twisting. Also
encourage him to use the screen scroll bars to ensure that what is being
viewed most is in the center of the monitor rather than at the top or
||At a height that doesn't make the user tilt
his head up or bend his neck down to see it. When seated comfortably,
a user should look at a point on the screen two to three inches below
the top of the monitor. If the monitor is too low, the user will crane
his neck forwards. If it's too high he'll tilt his head backwards and
end up with neck/shoulder pain.
||At a comfortable horizontal distance for
viewing, which is approximately an arms length (when you sit back
in your chair and raise your arm, your fingers should touch the screen).
At this distance you shouldnt need to move your head to see the
viewing area of the monitor. If text looks too small, use a larger font
or magnify the screen image in the software. Dont sit closer to
||In some instances and for some users, such
as those who wear bifocal corrective glasses, tilted backwards and the
height adjusted for comfortable screen viewing.
Where will the computer be used?
Think about the following environmental conditions.
Bright light glare should never be noticeable on the computer screen. If it
is, move the screen, lower the light level and get a good-quality, glass anti-glare
screen. Also make sure that the computer monitor screen isn't backed to a
bright window or facing a bright window (use a shade or drapes to control
Ideally, you should have adequate fresh-air ventilation and adequate heating
or cooling so you feel comfortable while you're working.
Noise can cause stress, which tenses your muscles and increases injury risks.
Try choosing a quiet place for your workstation, and use low-volume music,
preferably light classical, to mask the hum of any fans or other sound sources.
What furniture will you use?
Make sure the computer and its peripherals are placed on a stable working surface
with adequate room for proper arrangement. If this work surface will also be
used for writing on paper, choose one thats between 28 and 30 inches above
the floor. You should consider attaching a keyboard/mouse-tray system to your
work surface. Choose a height-adjustable system that allows you to tilt the
keyboard away from you slightly for better wrist posture (negative tilt). When
using the mouse, keep your upper arms relaxed and as close to the body as possible.
What chair will
If only one person is using the workstation, the chair can be at a fixed height.
But it should be comfortable to sit on and have a good backrest. If more than
one person will be using the computer, consider buying a chair with ergonomic
Why is posture important?
Good posture is the basis of good workstation ergonomics and the best way to
avoid a computer-related injury.
||The user should be able to reach the keyboard
keys with his wrists as flat (not bent up or down) and straight (not
bent left or right) as possible
||The user's elbow angle (the angle between
the inner surface of the upper arm and the forearm) should be at or
greater than 90 degrees, which will help avoid nerve compression at
||The upper arm and elbow must be as close
to the body and as relaxed as possible for mouse use. Avoid overreaching.
Also make sure that the wrist is as straight as possible when the mouse
is being used.
||The user must sit back in the chair and have
good back support. Also check that the feet can be placed flat on the
floor or on a footrest.
||Place frequently used items closer to the
user so they can be reached comfortably
||The users body should be centered on
the alphanumeric keyboard. Most modern keyboards are asymmetrical in
design (the alphanumeric keyboard is to the left and a numeric keypad
to the right). If the outer edges of the keyboard are used to center
the keyboard and monitor, the users hands will be deviated because
the alphanumeric keys will be to the left of the user's midline.
||Ensure that the head and neck are as straight as possible
Are work breaks important?
All ergonomists agree that it's a good idea to take frequent, brief rest breaks.
Practice the following:
Looking at a computer screen changes how the eyes work, causes you
to blink less often and exposes more of the eye surface to the air. Every
15 minutes you should briefly look away from the screen for a minute or two
to a more distant scene, preferably something more than 20 feet away. This
lets the muscles inside the eye relax. Also, blink your eyes rapidly for a
few seconds. This refreshes the tear film and clears dust from the eye surface.
Most typing is done in bursts rather than continuously. Between these bursts
of activity you should rest your hands in a relaxed, flat, straight position.
Every 30 to 60 minutes you should take a brief rest break. Stand up, move
around and do something else. Go and get a drink of water, soda, tea, coffee
or whatever. Youll exercise different muscles and feel less tired.
breaks. There are many stretching and gentle exercises
that you can do to help relieve muscle fatigue. You should do these every
one to two hours. Here are some examples.
Working at a computer can be hypnotic, and often you don't realize how long
you've been working and how much you've been typing and mousing. You can get
excellent ergonomic software to install on your computer. The best software
runs in the background and monitors how long you've been using the computer.
It will prompt you to take a rest break at appropriate intervals and will
suggest simple exercises.
||About Professor Alan Hedge, PhD,
Alan Hedge is a full professor in the Department of Design and
Environmental Analysis, Cornell University, where, since 1987, he has directed
the human factors and ergonomics teaching and research programs. Prior to
that, for over 10 years he ran the graduate program in applied psychology
and ergonomics at Aston University, Birmingham, UK. From 1990 to 1993 he
was also an Honorary Research Fellow at the Institute of Occupational Health,
University of Birmingham, UK.
His research and teaching activities have focused on issues of
design and workplace ergonomics as these affect the health, comfort and productivity
of workers. He is currently conducting research on carpal tunnel syndrome risk
factors for workers, alternative keyboard system designs, the performance and
health effects of postural strain, and on the health and comfort impacts of
environmental stressors, such as the effects of indoor air quality on sick building
syndrome complaints among office workers, and the effects of office lighting
on eyestrain problems among computer workers. He has published a book, 18 chapters
and over 130 articles on these topics in ergonomics and related journals.
For more information, visit Cornell University Ergonomics Web site.
Photos courtesy of Herman Miller - www.hermanmiller.com and
SMED International - www.smednet.com.